The present invention relates to a storage system, computer system and interface module and, more particularly, to a storage system, computer system, and interface module enabling switching across communication protocols for communicating with external devices.
FC-SAN using Fibre Channel (FC) nowadays prevails as a data transmission protocol for realizing Storage Area Networks (SANs). The Fibre Channel has performance of gigabits class to enable high-speed data transfer, and can be used for long-range connection by using optical fibers. Further, the Fibre Channel enables consolidating the management of storage systems associated with servers, making use of its feature that it can construct a network by employing interconnect devices such as switches.
Recently, a new storage networking technology based on an Internet Protocol (IP) has come out. Ethernet (a registered trademark), which has lagged behind the Fibre Channel in transfer performance, has succeeded in realizing Gigabit Ethernet with a data transfer rate that is made higher by applying the Fibre Channel's physical layer and data encoding mechanism that enable data transfer of gigabits class. Consequently, Ethernet now has a position competitive with the Fibre Channel in the storage networking field. The IP based storage networking technology is called an IP-SAN in distinction from the FC-SAN based on the Fibre Channel.
Turning to storage systems, on the other hand, lately, competitive vendors have keenly competed with each other in developing storage management solutions with higher functionality in addition to competing in terms of higher performance, larger capacity, and lower cost. Moreover, a variety of interfaces for connecting a storage system with computers (hereinafter referred to as hosts or servers) have been used. As the interfaces for connection with hosts, there exists ESCON and FICON which are main frame channel interfaces and Fibre Channel and Ethernet which are the above-mentioned open systems. For the storage systems, connectivity with servers is an important factor and plural kinds of module boards corresponding to the kinds of interfaces are prepared so that the storage systems can adapt to the above variety of interfaces.
The Fibre Channel and the Gigabit Ethernet operate at different data transmission rates in bits per second; Fibre Channel operates at 1.0625 Gbps, and Gigabit Ethernet operates at 1.25 Gbps. Now, the Fibre Channel has achieved a transmission rate of 2 Gbps. Bus adapters of switch and host are made to automatically correspond to a 1-Gbps (exactly, 1.0625 Gbps) Fibre Channel and a 2-Gbps Fibre Channel by detecting the transmission rate. This function of automatically detecting the channel transmission rate is generally called an auto-negotiation.
Although the data transmission rates of the Fibre Channel and the Gigabit Ethernet differ as described above, both the Fibre Channel and the Gigabit Ethernet use the same frequency of 106.25 MHz as a basic frequency of clocks for data acquisition timing. Moreover, the Fibre Channel adopts a method called a double data rate which acquires data at the rising and falling edges of each clock for 1 Gbps.
As one of prior art documents relevant to these technologies, for example, there is a JP-A No. 2002-318782.